Analysis and Design of PLL Motor Speed Control System

Transcription

1 TELKOMNIKA, Vol. 11, No. 10, October 2013, pp ~ 5668 ISSN: Analysis and Design of PLL Motor Speed Control System Qi chao Zhang Physics & Electronic engineering institute, Hubei University of Arts and Science Xiangying, China zqc3992@qq.com Abstract Phase-locked technology in motor speed control system has a wide range of applications. Especially for high accuracy in the motor steady speed operation situation, more and more use of phaselocked servo control system. This paper describes the block diagram and mathematical model of phaselocked control system, Shows the circuit parameter calculation method. This and combined with design example analysis of phase-locked control system, Indicated through the theory and practice, using PLL can obtain good speed control precision. Keywords: Phase-locked technology, motor speed, PFD Copyright 2013 Universitas Ahmad Dahlan. All rights reserved. 1. Introduction With the development of digital integrated circuit to reduce cost and phase-locked technology, Phase-locked technology is gradually widely used in motor speed control. Especially in the multi-motor keeps dragging system synchronous operation of, Using the phase-locked loop control, not only make the system has the advantages of simple structure, but also can obtain the control precision is very high. [1, 3] 2. The System Diagram and Mathematical Control Model Motor speed control system of phase-locked control principle block diagram is shown in Figure 1. The input signal to a system for a certain frequency of the square wave signal. The corresponding frequency and motor given speed, system output is the actual motor speed. Feedback component is the role of the speed signal into frequency and speed is proportional to the square wave signal. There can be multiple ways, generally uses the photoelectric device. If the motor speed is n, the motor speed to a week, pulse photoelectric device outputs the N offset, the feedback component output square wave angular frequency: Figure 1. Phase-locked control motor speed control system block diagram So the system the signal given by the angular frequency ω and the desired speed is: Comparison of ωr, ωf to PFD in frequency, phase, frequency difference and phase difference has the following relationship: (1) Received April 26, 2013; Revised June 28, 2013; Accepted July 13, 2013

2 5663 ISSN: (2) Type (2) for the Laplace transform, too Set the integration time is from ωr, ωf first began with equal, and the initial phase difference In the time after t0, when ωr equal to ωf, PFD generally use the CD4046. Analysis of the internal circuit, the equivalent circuit can be dotted line in Figure 2 on the left side of the said its function. [2] (3) Figure 2. The principle of CD4060 model and the PI control circuit (1) when ωf < ωr, K 1 conduction, K 2 showed high impedance. (2) when the ωf > ωr, K 2 conduction, K 1 showed high impedance. (3) when the ω f = ω r, if f = r is K 1, K 2 showed high impedance. If f < r K 2 showed high impedance, In a cycle of T T /2π time, K 1 conduction, the rest of the time showed a high impedance. If f > r K 1 showed high impedance, in a cycle of T T /2π time, K 2 conduction, the rest of the time showed high resistance. In order to said change detection, Using the circuit of the broken line to the right of Figure 2. Current flowing through the R on the I average value is proportional to the, As shown in Figure 3a, This is obviously the saturated nonlinear relationship. That is, i e is a pulse width and is proportional to the square wave signal, As shown in Figure 3b, Its AC component of the impact on the performance of the system will be, and should try to filter out. In fact, due to the inertia of the electromechanical system itself and of the PI controller used in the low-pass characteristic. As long as the suitably selected N can wherein the AC component is substantially attenuated. Figure 3. Waveforms In order to make the i e pulse height in positive and negative, are equal.therefore appropriate to adjust the U + value, So that V e -1.4-U + = U , That U + =( V e ) /2, Usually V e =5V, The U V, so the slope of the linear region, TELKOMNIKA Vol. 11, No. 10, October 2013 :

3 TELKOMNIKA ISSN: In fact, the frequency characteristic of the CD4046 is shown in Figure 3a,because the frequency difference type (3) of the internal connection. According to the circuit of PI controller (4) order R 2 C= T i then: (5) It should be noted that the PI controller is not connected to the inverter, the speed should a given square wave signal is connected to the MC4046's s end. The feedback signal is connected to the r end, otherwise it will form a positive feedback. Amplification driver for the K d, (6) the transfer function for DC motor: Wherein T m and T e, respectively, the mechanical time constant of the motor and the electrical time constant, Ignore T e, [5] (7) Figure 4. A system configuration diagram Described by the transfer function of the system structure shown in Figure 4. Linear range, the open-loop transfer function: (8) This shows that this is a typical third-order system. (9) 3. Determine the Best Open-Loop Model Parameters of a Typical Third-Order System Typical third order based on the frequency characteristics of, and the best open-loop model parameters are determined as follows:see Figure 5. system configuration diagram with logarithmic frequency characteristic, a typical third-order system structure shown in Figure 5a. is shown, corresponding to the ring-opening logarithmic frequency characteristic shown in Figure 5b. as shown. [4] Analysis and Design of PLL Motor Speed Control System (Qi chao Zhang)

4 5665 ISSN: Figure 5. System structure diagram with logarithmic frequency characteristics The characteristic is determined by three parameters, That ω 1 =1 / T 1, ω 0 and ω 2 =1 / T 2 Usually make: h=ω 2 /ω 1 =T 1 /T 2 (10) h is called the IF width, the band plays a decisive role in the dynamic performance, h is an important parameter of the typical third-order system. It can be proved to make the system stable, must be satisfied: h> 1 (11) ω 0 is the system of open-loop frequency cut-off angle is easy to prove that when ω 0 is ω 1, ω 2 geometric midpoint when to get the maximum amount of phase margin, that is, when (12) When ω 0, ω 1, ω 2 are determined, the open-loop amplification K is also determined, and can be obtained from Figure 6.: K = ω 0 ω 1 (14) (13) Substituting (11), substituting (12) into (14), we have: In this case, a typical third-order system of the open-loop transfer function can be represented by the T 2 and h: (15) Figure 6. The frequency and the parameters of a typical third-order system TELKOMNIKA Vol. 11, No. 10, October 2013 :

5 TELKOMNIKA ISSN: Figure 7. Step response of a typical third-order system Figure 7 [2, 7] is the use of computer to get different h when the closed-loop step response curve, IF width h respectively taken as 2.5, 3, 4, 5, 7.5 and the 10.The schedule given different performance indexes of the H value, from which we can see that, when h = 4~7. 5 indicators is better, generally take h = Calculation of Parameters in the Control System of Motor Phase-Locked 4.1. Determine the Integral Time and Open Loop Gain: Take h=5 Then h=t 1 /T m,t 1 =5T m (16) 4.2. To Determine the Parameter of Each Component 1. The choice of N: The i e contains the AC component of the fundamental frequency ω r, seen by the open loop frequency characteristics of the system, the number ω r > ω 2 in these AC component can greatly attenuated, Since ω r = Nω c, ω c is the angular frequency of the desired output of the system. If the design of speed control system, the minimum steady speed run speed ω min, Then the Nω min >ω 2 N>ω 2 /ω min (18) (17) general N = 1.5 ω 2 /ω min 2. The determination of the R 1, R 2, C: Integrated type (4), (5), (9) have: Analysis and Design of PLL Motor Speed Control System (Qi chao Zhang)

6 5667 ISSN: Type N, T i, have been identified, K d, K m is known or can be measured through the experiment, The equations (19) have three unknowns R 1, R 2, C, Give one of them to determine the appropriate value according to the specific circumstances and can solve for the remaining two component values. (19) 5. Examples of Application Design a motor phase-locked speed control system, the requirements of the load constant speed rotation, Motor speed error is less than 1/1000, the experimental validation even with high-precision regulated power supply powering the motor to reach the above requirements, using PLL design of motor speed error is only 1/3000.The principle of control circuit as shown in Figure 8. [6, 8] Figure 8. Principles of control circuit diagram The reference frequency after 10 4 divide by 2MH Z crystal oscillator sent to the CD feet. Motors rotate the encoder 64 pulses enlarged plastic divider (divide by 16) sent to the CD4046 pin 3 as the feedback signal. CD4046 CMOS PLL chip structure.there are two internal phase comparator, ω f ω r to PFD in frequency, phase comparison by the pin 13 output error voltage U d,the loop filter is the active proportional integral filter to ensure the stable operation of the phase-locked loop op amp. When the loop is locked r advance f 1/4 cycle K 1 (s) = 20. When considering the role of the loop filter, the entire control loop is a third-order system. In order to ensure the stable operation of the system, the loop filter must have a leading phase correction function,here the choice the active proportional integral filter, Bode plots analysis taken: T 1 = R 1 C 1 = 56k 200 = 11.2s, T 2 = R 2 C 1 = 5k 200 = 1s.While f r changes in the range of 115~225H Z, the system stable work. The K 1 value directly affect the size of, phase lag difference and motor stable rotating speed range. K 1 becomes larger, the smaller, system transition time is short, and the overshoot. While the K 1 value is too large, so that the lower limit of f r value change tracking system; The smaller value of K 1, becomes large, the system transition time is long, but the K 1 value is too small, the upper bound of the system f r to track the value of smaller. So that the system timing belt narrowing, Debugging with an oscilloscope to observe the CD4046 first pin voltage waveform, Adjust the value of K 1 f r lags behind the f r the phase control in less than 45 o is appropriate, system stability, All levels of output voltage waveform is shown in Figure 9. [9] TELKOMNIKA Vol. 11, No. 10, October 2013 :

7 TELKOMNIKA ISSN: Figure 9. Levels of waveform Motor with a brush motor,brush sparks easy to interfere with the signal output of the encoder assembly. Therefore, filtering and other measures should be taken to eliminate, clean fr signal. [10] Otherwise, the loop not work stable.if the motor excitation voltage of U 2 wave has a high frequency interference. The U 2 side parallel to appropriate capacitance eliminate. If the fixed frequency divider into a programmable frequency divider. Adjust the speed of the motor can be achieved, has good prospect of application. References [1] Xing Ping Wan, Jusheng Zhang, Jiyu Zheng. Phase-Lock Technology. Xian University of Electronic Science and Technology Press; (1989) [2] Guanbai zhang. Phase-locked frequency synthesis technology. Beijing: Electronic Industry Press; 1990 [3] Roland E Best. Phase-locked loop design simulation and applications. Beijing: Tsinghua University Press; (2003). [4] Feng Xue, Jie Guan. Phase-locked motor speed control system. Overview in: Micro motor. 1999; 32(3): [5] Xingzhong Deng: Electric drive control Wuhan. Huazhong University of Science and Technology Press; (2001). [6] Zhiwei Huang. Phase-locked loop frequency synthesizer circuit design. Xian University of Electronic Science and Technology Press; (2008). [7] Guixuan Zhu. Enery Saving Application of Pump and Blower Speed Regulation. China Well and Rock Salt. 2010; 37: [8] Dong Guan, Xiao-hui Yang. Simulation Study on Critical Speed of Rotor for High-Speed PM Motors. Shanghai: Small & Special Electrical Machines, China. 2013; 2(41). [9] Yuanshen Zhou. AC and DC Speed Control System Simulation with MATLAB. China Electric Power Press; [10] ianzhu Mu, Chunsong Liu, Xuan Hu. Application of Speed Estimates on High-Voltage Motor Drive Energy Saving. Electric Machines & Control Application, China. 2013; 1(40.1). [11] Xuan Cui Yuan, Ji Hua Sun. A Research on Dynamic Friction Compensation of High-speed Linear motor. TELKOMNIKA Indonesian Journal of Electrical Engineering. 2012; 10(8). [12] Reza Ilka, S. Asghar Gholamian. Optimum Design of a Five-Phase Permanent Magnet Synchronous Motor for Underwater Vehicles by use of Particle Swarm Optimization. TELKOMNIKA Indonesian Journal of Electrical Engineering. 2012; 10(5): Analysis and Design of PLL Motor Speed Control System (Qi chao Zhang)